Christoph Manke

On the heating of linear conductive structures as guide wires and catheters in interventional MRI

The interest in performing vascular interventions under magnetic resonance (MR) guidance has initiated the evaluation of the potential hazard of long conductive wires and catheters. The objective of this work is to present a simple analytical approach to address this concern and to demonstrate the agreement with experimental results. The first hypothesis is that a long conductive structure couples with the electric field of the radio frequency (RF) transmit coil. The second hypothesis is that this coupling induces high voltages near the wire ends. These voltages can cause tissue heating due to induced currents. The experimental results show an increase in coupling when moving a guide wire toward the wall of an RF transmit coil, documented with a temperature increase of a saline solution in close proximity to the tip of the guide wire. The coupling of the wire not only presents a potential hazard to the patient, but also interferes with the visualization of the wire. A safe alternative would be the use of nonconducting guide wires. J. Magn. Reson. Imaging 2001;13:105–114.

Corrosion of tungsten coils after peripheral vascular embolization therapy: influence on outcome and tungsten load.

The purpose of this study was to evaluate coil corrosion and the long‐term outcome after peripheral vascular embolization therapy performed with tungsten coils. We studied 14 patients who received tungsten coils on an average of 26 months prior to follow‐up. The protocol included plain radiography and contrast‐enhanced magnetic resonance angiography to investigate corrosion of tungsten coils and recanalization of the embolized vessels. Whole blood, hair, and urine tungsten levels were assayed when available. Corrosion of tungsten coils was detected in 9 of 14 patients by plain radiography. No evidence of recanalization of the embolized vessel and no adverse clinical effects of tungsten resorption were detected. Blood levels of tungsten were elevated in 6 of 14 patients and urine levels of tungsten were elevated in all 12 patients tested. Tungsten coil corrosion and elevated tungsten levels in blood, hair, and urine were found in most patients, although no adverse clinical effects of tungsten resorption were detected. Since the overall effect of high tungsten blood levels remains unclear, its use as an implant should be avoided. Catheter Cardiovasc Interv 2004;62:380–384.

Peripheral Arterial Balloon Angioplasty: Effect of Short versus Long Balloon Inflation Times on the Morphologic Results

PURPOSE To evaluate the effect of different balloon inflation times on angiographic results in peripheral angioplasty. MATERIALS AND METHODS Seventy-four infrainguinal arteriosclerotic lesions were randomized prospectively to undergo balloon dilation for 30 seconds (group I) or 180 seconds (group II). Each group consisted of 37 patients. Postinterventional angiograms were evaluated by two blinded readers. Dissections were graded as follows: 1 = no dissection; 2 = minor flap; 3 = extensive dissection membrane, not flow limiting; or 4 = flow-limiting flap. The rate of major-grade dissections (grades 3 and 4), residual stenosis (>30%), and further interventions were compared with the two-tailed chi(2) test. RESULTS In group I, major dissections were noted in 16 patients (43%) compared with five patients (14%) in group II (P =.009). Residual stenoses were found in 12 patients (32%) in group I compared with five patients (14%) in group II (P =.096). The rate of additional interventions was significantly higher in group I than in group II (20 of 37 vs nine of 37; P =.017). CONCLUSION A prolonged inflation time of 180 seconds improves the immediate angioplasty result of infrainguinal lesions compared to a short dilation strategy. Significantly fewer major dissections and a modest reduction of residual stenoses are observed. The requirement of costly and time-consuming further interventions is significantly reduced.

FLAT-PANEL X-RAY DETECTOR USING AMORPHOUS SILICON TECHNOLOGY : REDUCED RADIATION DOSE FOR THE DETECTION OF FOREIGN BODIES

RATIONALE AND OBJECTIVES The authors evaluate a new flat-panel x-ray detector (FD) with respect to foreign body detection and reduction of radiation dose compared with screen-film radiography. METHODS Flat-panel x-ray detector is based on amorphous silicon technology and uses a 1 k x 1 k photo-detector matrix with a pixel size of 143 x 143 microns and 12-bit digital output. A thallium-dotted cesium iodide scintillation layer converts x-rays into light. An ex vivo experimental model was used to determine the detectability of foreign bodies. Foreign bodies with varying sizes were examined: glass with and without addition of lead, bone, aluminium, iron, copper, gravel fragments, and graphite. Four hundred observation fields were examined using conventional radiography (speed, 400; system dose: 2.5 microGy) as well as FD with a simulated speed of 400, 800, 1200, and 1600, corresponding to a detector dose of 2.5 microGy, 1.25 microGy, 0.87 microGy, and 0.625 microGy, respectively. Four independent radiologists performed receiver operating characteristic analysis of 8000 observations. RESULTS Flat-panel x-ray detector with a simulated speed of 400 was significantly superior (P = 0.012) to screen-film radiography (speed, 400). At a simulated speed of 800 and 1200 FD yielded results equivalent to screen-film radiography. Flat-panel x-ray detector was significantly inferior to screen-film radiography at a simulated speed of 1600 (P = 0.012). CONCLUSIONS Flat-panel x-ray detector technology allows significant reduction in radiation dose compared with screen-film radiography without loss of diagnostic accuracy.

Radiologische Implantation zentralvenöser Portsysteme am Unterarm

PURPOSE To retrospectively analyze the technical result and long term outcome of central venous arm ports placed by radiologists. MATERIALS AND METHOD Over a 5-year period, 399 arm ports were implanted by radiologists in 391 patients. The system consists of a low profile titanium chamber and a silicone catheter. Ports were placed at the forearm after puncture of a vein proximally to the elbow under fluoroscopic guidance. In a retrospective analysis the technical results and the long term outcome were evaluated. Complications were documented according to the standards of the society of interventional radiology. RESULTS In 391 patients a total of 98 633 catheter days were documented (1 - 1325 days, mean 252 days). Primary technical success was 99.25 % (396 / 399) with a 100 % secondary technical success rate. No severe procedural complications, e. g. pneumothorax or severe hemorrhage, were found. A total of 45 complications occurred (11.28 %, 0.45 / 1000 catheter days), including 8 portal pocket infections (27 - 205 days, mean 115 days). Fifteen ports were explanted because of complications. The complication rate corresponds to the data from subclavian ports and is less than the complication rates published in large surgical trials. CONCLUSION Implantation of central-venous arm ports by radiologists is safe and minimally invasive. No severe immediate procedural complications occur due to the peripheral implantation site. Long term complication rates are comparable to other studies of radiological or surgical port implantation at different sites.

Magnetic resonance monitoring of stent deployment: in vitro evaluation of different stent designs and stent delivery systems.

RATIONALE AND OBJECTIVES To evaluate MR imaging features of commercially available stents before, during, and after in vitro deployment as a step toward MR-guided stent deployment. METHODS Fourteen stents were deployed in a phantom under MR monitoring at 1.5 T by using a gradient-echo sequence. Device visibility was rated on a four-point scale (excellent, fair, poor, not visible). RESULTS The Memotherm stent and the rolling membrane (RM) Wallstent showed excellent stent visibility and at least fair scores for artifact-induced narrowing of the stent lumen. Three stents (Palmaz, AVE, Easy Wallstent) showed excellent visibility of the stent but no visible lumen. Five stents (Strecker, Accuflex, Hemobahn, Passager, Sinus) displayed fair visibility. The delivery catheters of four stent systems (Smart, Vascucoil, Symphony, ZA) displayed severe black hole artifacts. CONCLUSIONS The imaging features of several stent systems might be suitable for MR-guided intervention. The Memotherm and the Wallstent RM combine good visibility of the stent and the lumen.

Appearance of vascular stents in computed tomographic angiography: in vitro examination of 14 different stent types.

Strotzer M, Lenhart M, Butz B, et al. Appearance of vascular stents in computed tomographic angiography: In vitro examination of 14 different stent types. Invest Radiol 2001; 36:652–658. rationale and objectives. To evaluate the appearance of the vessel lumen after implantation of different vascular stents with the use of a computed tomographic (CT) angiography model. methods.A vascular phantom was studied with helical CT and different slice thicknesses (2 and 3 mm) and pitch values (1.0, 1.5, and 2.0). Original transverse CT images and coronal reformations were evaluated. Fourteen different stents were analyzed with regard to changes in the stent lumen (attenuation values, noise, and artificial lumen narrowing). results.Some stents caused artifacts resulting in potential errors during evaluation of their patency. Assessment of the lumen was impaired in two stents (Strecker tantalum and Passager). Increased attenuation values were measured in all stents (increase of 8%–145%). The degree of artificial lumen narrowing was 4.4% to 77.8%. conclusions.In most stents, reliable evaluation of the stent lumen seems possible. However, knowledge of the artifacts caused by different stent types is useful for the assessment of stent patency with CT angiography.

Post-traumatic pseudocyst of the spleen: Sclerotherapy with ethanol

We report a case of successful percutaneous treatment of a chronic post-traumatic splenic pseudocyst using alcohol as the sclerosing agent. A 26-year-old man presented with a symptomatic cystic mass located in the spleen. Aspiration of 300 ml of fluid was only temporarily effective, and therefore a drainage catheter was placed 3 days later. After histopathologic and microbiologic exclusion of a malignant or infectious origin, local sclerotherapy with alcohol was performed because of recurrence after percutaneous drainage. This therapy was repeated six times within 2 weeks. Two weeks later, the remaining volume was determined to be 16 ml. Six months after treatment the cyst was no longer visible. To our knowledge this is the first case of a chronic post-traumatic splenic cyst treated with alcohol. Percutaneous sclerotherapy of a symptomatic post-traumatic splenic pseudocyst may be an alternative to surgical treatment.

Karotisendarteriektomie und Karotisstenting : Pilotstudie eines prospektiven, randomisierten und kontrollierten Vergleichs

ZusammenfassungFragestellung. In einer prospektiven, randomisierten und kontrollierten Pilotstudie werden die Karotisendarteriektomie und die Stenttherapie an einem Patientenkollektiv mit hochgradigen, symptomatischen Stenosen der extrakraniellen A. carotis interna miteinander verglichen. Methodik. Das Design der Studie sieht vor, dass symptomatische Patienten mit der Diagnose einer hochgradigen Stenose (≥70%) der A. carotis interna, die auf dem Boden einer DSA gesichert wurde, eingeschlossen werden. Vor und nach der Therapie finden während der Hospitalisationsphase jeweils eine klinisch-neurologische Untersuchung, eine Duplexsonographie der Hals- und Hirngefäße und eine MRT des Hirns statt. Das Nachsorgeprotokoll nach 1, 6 und 12 Monaten beinhaltet jeweils eine klinisch-neurologische Untersuchung und eine Duplexsonographie sowie nach 12 Monaten zusätzlich eine selektive Angiographie der behandelten Seite und eine weitere MRT des Hirns. Während eines Zeitraums von 9 Monaten wurden bisher 23 von 137 wegen einer Karotisstenose behandelten Patienten in die Studie eingeschlossen, wobei 11 Patienten dem operativen Arm und 12 Patienten dem interventionellen Arm der Studie zugeführt wurden. Ergebnisse. Bei allen 23 Patienten wurde ein Primärerfolg ohne residuelle Stenose >30% erzielt, eine zerebrale Ischämie oder Todesfall traten nicht auf. Die bislang durchgeführten 18 Nachuntersuchungen (neurologische Untersuchung einschließlich Duplexsonographie) bei insgesamt 13 Patienten (13 Kontrollen nach 30 Tagen, 5 Kontrollen nach 6 Monaten) ergaben keine relevante Restenosierung und keine zerebrale Ischämie. Schlussfolgerung. Bislang erwies sich die Stenttherapie in unserer Studie als komplikationsarmes Therapieverfahren. Aufgrund der geringen Patientenzahl kann zum jetzigen Zeitpunkt jedoch noch keine endgültige Bewertung erfolgen.AbstractIntroduction. A prospective, randomized and controlled trial is conducted to compare carotid endarterectomy and carotid stenting in high grade symptomatic carotid artery stenoses. Methods. According to the study design symptomatic patients with a angiographically highgrade (≥70%) internal carotid artery stenosis are included. Pre- and postinterventional diagnostics during the hospitalization period includes neurological assessment, duplex sonography of the cervical and cerebral arteries and magnetic resonance imaging of the brain. Follow-up examinations are scheduled after 1, 6 and 12 months and consist of a neurological assessment and duplex sonography. After 12 months selective angiography and magnetic resonance imaging of the brain will be performed additionally. During a period of 9 months up to now 23/137 patients treated for a carotid artery stenosis were included in the study, 11 patients underwent surgery and 12 patients carotid stenting. Results. Carotid stenting and endarterectomy was primarily successful without residual stenosis >30% in each patient without the occurence of stroke or death. In 18 follow-up examinations (neurological assessment including duplex sonography) of 13 patients (13 follow-up examinations after 30 days, 5 after 6 months) no relevant restenosis and no stroke occured. Conclusion. As of yet, carotid stenting was a safe procedure. Due to the small number of patients a definitive conclusion can not be drawn.

Temporary strecker stent for management of acute dissection in popliteal and crural arteries

Stent placement is a widely used bail-out treatment for dissection of peripheral arteries. Below the level of the superficial femoral artery permanent stenting is complicated by a high incidence of subacute thrombosis and restenosis. We present two cases of arterial occlusion due to acute iatrogenic dissection of the popliteal and distal fibular arteries. Successful treatment was achieved with a new bail-out procedure. Strecker stents were implanted to seal off the dissection flap. Stents were retrieved easily after 24 hr using a myocardial biopsy forceps. After stent retrieval the temporarily stented segments were patent and showed a larger lumen compared with segments treated by balloon dilatation alone. Temporary stenting is a simple and safe procedure and offers the advantage of tacking up dissection membranes and preventing recoil. Persistent presence of a metallic implant as a source of continued injury and stimulus for intimal proliferation is avoided.